几道常用最新最基本的JAVA笔试题目.doc

1、求一个数的阶乘： /* * 递归算法 * param number 某个数 * return 某个数的阶乘 */public static long recursion(int number) /非法时 if(number 0) return -1; /1,0的阶乘等于1 if(number 2) return 1; return number*recursion(number-1);/* * 非递归算法 * param number 某个数 * return 某个数的阶乘 */public static long noRecursion(int number) /number的阶乘值，默认为1 long result = 1 ; /非法时 if(number 0) return -1; /1,0的阶乘等于1 if(number 2) return 1; for(int i = 1; i=number; i+) result *= i; return result;2、两数交换： /* * 两个数交换：方法一(不用第三方变量) 【注：此方法在不保证在其他语言中有效】 * param x * param y */ public static void toSwap1(int x, int y) y = x - 0 * (x = y); System.out.println(x = + x); System.out.println(y = + y); /* * 两个数交换：方法二(不用第三方变量) * param x * param y */ public static void toSwap2(int x, int y) x = y; y = x; x = y; System.out.println(x = + x); System.out.println(y = + y); /* * 两个数交换：方法三(使用第三方变量) * param x * param y */ public static void toSwap3(int x, int y) int temp; temp = x; x = y; y = temp; System.out.println(x = + x); System.out.println(y = + y);3、排序： /* * 冒泡排序 * param numbers int型数组 */ public static void bubbleSort(int numbers) /交换数时用的临时变量 int temp; /数组长度 int size = numbers.length; for (int i = 0; i size - 1; i+) for (int j = i + 1; j numbersj) temp = numbersi; numbersi = numbersj; numbersj = temp; for (int i = 0; i numbers.length; i+) System.out.println(numbersi); /* * 快速排序 * param numbers int型数组 * param start * param end */ public static void quickSort(int numbers, int start, int end) if (start end) / 选定的基准值(第一个数值作为基准值) int base = numbersstart; / 交换数时用的临时变量 int temp; int i = start, j = end; do while (numbersi base) & (i base) & (j start) j-; if (i = j) temp = numbersi; numbersi = numbersj; numbersj = temp; i+; j-; while (i = j); if (start i) quickSort(numbers, i, end); for (int i = 0; i numbers.length; i+) System.out.println(numbersi); /* * 选择排序 * param numbers int型数组 */ public static void selectSort(int numbers) / 交换数时用的临时变量 int temp; /数组长度 int size = numbers.length; for (int i = 0; i i; j-) if (numbersj numbersk) k = j; temp = numbersi; numbersi = numbersk; numbersk = temp; for (int i = 0; i numbers.length; i+) System.out.println(numbersi); /* * 插入排序 * param numbers int型数组 */ public static void insertSort(int numbers) / 交换数时用的临时变量 int temp; /数组长度 int size = numbers.length; int j; for (int i = 1; i 0 & temp numbersj - 1; j-) numbersj = numbersj - 1; numbersj = temp; for (int i = 0; i numbers.length; i+) System.out.println(numbersi); /* * 归并排序 * param numbers * param left * param right */ public static void mergeSort(int numbers, int left, int right) / 每组元素个数 int t = 1; int size = right - left + 1; while (t size) int s = t;/ 本次循环每组元素个数 t = 2 * s; int i = left; while (i + (t - 1) size) merge(numbers, i, i + (s - 1), i + (t - 1); i += t; if (i + (s - 1) right) merge(numbers, i, i + (s - 1), right); for (int i = 0; i numbers.length; i+) System.out.println(numbersi); /* * 归并算法实现 * param data * param p * param q * param r */ private static void merge(int data, int p, int q, int r) int B = new intdata.length; int s = p; int t = q + 1; int k = p; while (s = q & t = r) if (datas = datat) Bk = datas; s+; else Bk = datat; t+; k+; if (s = q + 1) Bk+ = datat+; else Bk+ = datas+; for (int i = p; i = r; i+) datai = Bi; for (int i = 0; i data.length; i+) System.out.println(datai); 4、数据翻转： /* * 非递归 * param str 需要转换的字符串 * return 翻转好的字符串 */ public static String turn(String str) char ch = str.toCharArray(); char temp; for (int i = 0; i (ch.length+1)/2; i+) temp = chi; chi = chch.length-i-1; chch.length-i-1 = temp; return new String(ch); /* * param str 需要反转的字符串 * return 反转好字符串 */ public static String reverse(String str) /如果小于2位，则返回本身 if(str.length() = 0; i-) sb.append(str.charAt(i); return sb